In photographic equipment such as film projectors, one or more light bulbs are used to illuminate an image for display. Occasionally, however, the bulb will burn out and require changing. It is common practice when changing the bulb to terminate power to the equipment in order to prevent accidental shock.
Furthermore, it is desirable to maximize the operating life of the bulb. It is known that a significant reduction in bulb life occurs during start-up when power is first applied to the bulb. This is because significant shock to the bulb filament occurs due to the initial surge of current reaching the filament when the light bulb is turned on.
A number of conventional apparatus for reducing an initial surge of current to a downstream load have been disclosed. For example, soft start circuits are described in U.S. Pat. No. 4,580,088 by Bloomer; as well as in U.S. Pat. No. 4,621,313 by Kiteley; and U.S. Pat. No. 3,243,689 by Perrins. Furthermore, variable duty cycle circuits have been described in U.S. Pat. No. 4,163,923 by Herbers et al; and in U.S. Pat. No. 4,439,820 by Kuhn et al.
In addition, a number of conventional light bulb socket assemblies have been disclosed. For example, various light bulb socket assemblies used in conjunction with printed circuit boards have been described in U.S. Pat. No. 4,152,622 by Fitzgerald; as well as in U.S. Pat. No. 4,076,358 by Taormina et al; in U.S. Pat. No. 3,555,341 by Curtis; and in U.S. Pat. No. 3,544,950 by Lopez et al.